1. Field of Invention
The present invention relates to torque regulation of torque tools, and more particularly to a torque regulating assembly which can provide a precise maximum value of torque output and prevent the maximum value of torque output of the torque regulating assembly from being changed by vibration or impact, which influences the actual torque output.
2. Related Art
In general, when a screwing element such as a screw or a nut is to be drive locked by turning a tool bit (screwdriver bit, bit holder etc.) via a torque tool, a proper torque must be used according to the specification of the screwing element and the requirement for the preload, thereby such a screwing element can be surely locked without any damage due to excessive torque applied by the torque tool. Meanwhile, excessive torque can also make the screwing element have excessive preload, thus reducing the maximum value of its bearable external load. To make the torque output of manually rotated torque tools such as grab handles, pneumatic tools, and motor driven tools reach a predetermined value, a torque regulating assembly is usually applied between the torque tool and the tool bit for torque transmission, thereby limiting the maximum torque output value-of the torque tool, such that the torque of the tool bit to the screwing element is restricted at the maximum when the screwing element is being tightened.
Referring to FIGS. 1A, 1B, 2A, 2B, and 3, a conventional torque regulating assembly includes a first tubular shell 1, a second tubular shell 2, a first coupling block 3, a second coupling block 4, an elastic element 5, and a torque regulating ring 6. The first tubular shell 1 is screwed into the second tubular shell 2 with threads, and a linear relative displacement of the second tubular shell 2 to the first tubular shell is generated via relative rotation. At least one groove 1a is disposed at the external wall of the first tubular shell 1 along the longitudinal axis of the first tubular shell 1. The second tubular shell 2 has at least one aperture 2a corresponding to the groove 1a. The first coupling block 3 and the second coupling block 4 are disposed in the internal space formed by the first tubular shell 1 and the second tubular shell 2 together, and they press against each other to form a frictional coupling relation. The first coupling block 3 is connected to a driving shaft 7, and the driving shaft 7 is connected to a power source (not shown), for example, a pneumatic device or a power motor, disposed inside the housing 8 of the torque tool. The second coupling block 4 is connected to an output shaft 9, and the front tip of the output shaft 9 can be connected to a tool bit 9a of any type as desired. After the driving shaft 7 is driven by the power source, the first coupling block 3 drives the second coupling block 4 to rotate for carrying out the torque transmission, making the output shaft 8 drive the tool bit 9a to tighten a screwing element (not shown). The coupling force between the first coupling block 3 and the second coupling block 4 is determined by the normal force between the first coupling block 3 and the second coupling block 4, and the coupling force can determine the maximum torque transmitted between the first coupling block-3 and the second coupling block 4. The elastic element 5 presses against the second coupling block 4 and the second tubular shell 2 respectively with two ends, for generating an elastic force to push the second coupling block 4 pressing against the first coupling block 3, so as to produce the aforementioned normal force. The torque regulating ring 6 is put around the second tubular shell 2. An elastic ring 6a is disposed in the regulating ring 6, just covering the aperture 2a, and pushes a positioning ball 6b into the groove 1a through the aperture 2a to move. The positioning ball 6b is partly located in the groove 1a, and partly located in the aperture 2a to fix the relative positions of the first tubular shell 1 and the second tubular shell 2, avoiding linear relative displacement between the first tubular shell 1 and the second tubular shell 2 due to their relative rotation, and meanwhile to fix the length of the elastic element 5, for generating a constant elastic force to push the second coupling block 4. If the torque transmitted by the first coupling block 3 and the second coupling block 4 is greater than the coupling force between them, the first coupling block 3 and the second coupling block 4 cannot be coupled with each other in time, resulting in idleness of the first coupling block 3, as shown in FIG. 3, therefore, they cannot transmit larger torque than predetermined, thereby the screwing element is tightened with a proper torque. By making the second tubular shell 2 rotate relative to the first tubular shell 1 to generate a linear relative displacement, the length of the elastic element 5 can be altered, so as to change the maximum value of the torque output by the torque tool. During the process, the positioning ball 6b first disengages from the groove 1a, slides along the outer surface of the first tubular shell 1, and then again engages into the groove 1a to fix the second tubular shell 2, thereby preventing the second tubular shell 2 from rotating relative to the first tubular shell 1 as the torque tool is operated. However, in the conventional torque regulating assembly, the design of using the elastic ring 6a to push the positioning ball 6b has the advantages of being easy to operate and the torque being able to be quickly switched without any tool, the elastic force of the elastic ring 6a cannot be changed in accordance with the working condition for improving the positioning effect of the positioning ball 6b. The impact and vibration occurring during tightening the screwing element often cause the positioning ball 6b to disengage from the groove 1a, making the second tubular shell 2 rotate relative to the first tubular shell 1 and resulting in a linear relative displacement, which changes the maximum value of the torque output and causes difficulty in usage. Besides, the elastic ring 6a may be elastic fatigue after long-term operation, thus it becomes more likely that the positioning ball 6b will disengage from the groove 1a. 